The fraud claim really isn't that important in the overall scheme of things but the fact that the attorneys for MBIA are arguing that Countrywide was the largest single cause of the bust shows how weak their arguments are. Ever hear of Fannie/Freddie guys?
Having said the above it would be interesting to see a good economist try to argue that Countrywide was responsible. Some have argued Fannie/Freddie are responsible but even there, there is significant dissent.
The only issue before the appellate court that I care about is the successor liability issue. That is merely one of the significant hurdles MBIA has to clear in order to collect anything.